Without limiting the scope of the present invention, its background is described with reference to providing communication and sensing during a gravel pack operation within a subterranean wellbore environment, as an example.
In the subterranean well completion and production arts, downhole tools are often lowered into a well completion assembly to perform a variety of tasks. For example, a downhole tool may be lowered into a gravel pack completion assembly to assist in installation of a part of the assembly or as part of other gravel packing operations. Generally, gravel packing operations involve placing a screen into a wellbore. Packers are set above and below the screen and the surrounding annulus is then packed with prepared gravel of a select size designed to inhibit the passage of formation sand. In addition to filtering formation fluids, such a system can help to stabilize the formation without adversely affecting well productivity.
When lowering the downhole tool into the gravel pack completion assembly, the tool must often be positioned at a specific axial location within the completion assembly. This positioning is often referred to as “locating” the downhole tool. To locate a downhole tool at a specific position in a gravel pack completion assembly can be a difficult task because the gravel pack completion assembly can be installed several thousand feet below the surface. When lowering such a downhole tool on a cable, measurement of the length of cable dropped into the wellbore has not been found to be an accurate measurement of the precise position of the downhole tool. Likewise, when lowering such a downhole tool on a tubing or pipe string, traditional locating collets used to land the tool can result in undesirable limits on the outer diameter of other equipment carried by the tubing string. Moreover, the use of J-slots as an alternative to collets introduces uncertainty as to whether the correct J-slot has been engaged and tends to require undesired manipulation of the tubing string through raising, rotating and lowering in order to navigate the J-slots. Accordingly, a need has arisen for an improved apparatus and method for locating downhole tools at a location within a completion.